Electrochemical mining apparatus

ABSTRACT

An electrode assembly is described for use in direct electrochemical extraction of metal values from subterranean sulfide ore deposits. The electrode assembly is designed for insertion into a well or shaft penetrating into an ore body beneath the earth&#39;&#39;s surface to effect electrolysis and recovery of metal values from the ore body. The electrode is comprised of titanium and preferably is designed for use as a cathode. Means are associated with the assembly for continuous or intermittent removal of precipitated metal values, the circulation of electrolyte and the isolation of the electrode within an electrolyte reservoir wherein the electrolysis takes place.

United States Patent Drinkard, Jr. et al.

[ ELECTROCHEMICAL MINING APPARATUS [75] Inventors: William F. Drinkard, .lr., Charlotte;

Henry S. Brown, Raleigh; Hans J. Woerner, Mount Pleasant, all of NC.

[73] Assignee: Mineral Research & Development Corporation, Charlotte, NC

[22] Filed: May 17, 1974 [21] Appl. No.: 470,809

[52] U.S. Cl 204/286; 204/105 R; 204/106; 204/109; 204/112; 204/114; 204/120; 204/233; 204/280; 204/282; 204/260; 204/275 [51] Int. Cl. Blllk 3/04; C22d 5/00 [58] Field of Search 204/105-122, 204/280, 282, 286, 233, 234, 260, 275

[56] References Cited UNITED STATES PATENTS 272,391 2/1883 Thiollier 204/96 [451 July 15,1975

Primary ExaminerF. C. Edmundson Attorney, Agent, or Firm-Herbert M. Adrian, Jr.

[57] ABSTRACT An electrode assembly is described for use in direct electrochemical extraction of metal values from subterranean sulfide ore deposits. The electrode assembly is designed for insertion into a well or shaft penetrating into an ore body beneath the earth's surface to effect electrolysis and recovery of metal values from the ore body. The electrode is comprised of titanium and preferably is designed for use as a cathode. Means are associated with the assembly for continuous or intermittent removal of precipitated metal values, the circulation of electrolyte and the isolation of the electrode within an electrolyte reservoir wherein the electrolysis takes place.

10 Claims, 4 Drawing Figures ELECTROCHEMICAL MINING APPARATUS INTRODUCTION This invention relates to the electrochemical mining of ore bodies positioned beneath the earth's surface, and more particularly to an electrode assembly particularly suited for the extraction of metal values from electrically conductive sulfide ore deposits.

BACKGROUND OF THE INVENTION It has previously been proposed to mine metal values directly from sulfide ores in place beneath the earths surface by electrochemical means. While this idea is feasible, previous attempts to accomplish this feat have not been sufficiently successful to be accepted commercially. In order to carry out such a process on an ef fective scale, various shortcomings in the previous methods must be overcome.

A particular problem that has hindered development of such procedures has been in providing a means for carrying out the electrolysis in a continuous uninterrupted manner with the minimum of maintenance and attendance. Such prior methods often recovered the metal values by plating the metal being recovered onto the electrode. Such a procedure requires periodic shutdowns and removal of the electrode from the electrolysis area to remove the metal values therefrom.

With recent improvements in electrochemical mining methods, such as reducing or eliminating electrode polarization, long-term electrolysis is now possible. Thus, the electrolysis could be continued indefinitely, barring the need to service the electrodes, and provided the metal values could be removed without removing the electrodes.

It is, therefore, an object of the present invention to provide an electrode assembly which can be placed within a subterranean electrolysis environment and operated for indefinite periods of time without servicing or removal.

It is another object of the present invention to provide an electrode assembly which greatly reduces or eliminates dilution of electrolytes with ground water seepage.

It is a further object of the present invention to provide an electrode assembly having means for the collection and recovery of precipitated metal values, the removal of such metal values from the subterranean electrolysis area and the circulation of electrolyte to and from such electrolysis area.

These and other objects of the present invention will become readily apparent to those skilled in the art from the description of the invention which follows.

THE INVENTION In accordance with the invention, an electrode assembly for the extraction of metal values from earthheld deposits is provided comprising a shaped structure of titanium having electrically conductive means for the passage of direct electrical energy attached to said titanium structure, said structure being enclosed in a perforated, nonconductive housing, said housing having a lower nonperforated enclosure for the collection of sediment, said enclosure having means for withdrawing sediment therefrom on a continuous or intermittent basis and said assembly additionally having means associated therewith for the return of replacement electrolyte.

In a more preferred embodiment of the present apparatus, seal means are positioned on the upper portion of the electrode assembly, said seal means preferably being expandable so as to form a liquid tight seal between the shaft or well walls and the electrode assembly, thereby preventing the passage of liquids such as water which may otherwise dilute the electrolyte. The utilization of titanium as the electrode material prevents metal values from adhering to the electrode and plating thereon during the electrolysis of the ore body. The titanium is nonadherent under the electrolysis conditions and results in the production of finely divided metal particles which settle to the bottom of the electrode assembly wherein they are collected for subsequent removal to the earths surface.

DETAILS OF THE INVENTION The invention will be more fully understood by reference to the drawings in which:

FIG. 1 is a longitudinal sectional view of an electrode assembly of the present invention;

FIG. 2 is a plan sectional view along lines 2-2 of FIG. 1',

FIG. 3 is another plan sectional view along lines 33 of FIG. 1; and

FIG. 4 is a partially exposed view of the apparatus of the present invention in position in a sulfide ore body beneath the earths surface.

Referring more particularly to FIG. I, electrode assembly 10 is comprised of a perforated, rigid, nonconductive housing 12 having a lower enclosure 14 suitable for the collection of sediment. Housing 12 is preferably cylindrical in shape and is composed of rigid plastic piping of suitable diameter having perforations, i.e., slots, pores or the like, to provide free liquid circulation therethrough. As with all of the nonconductive parts utilized herein. plastic materials are the most preferred.

Numerous different plastic materials can be used provided they are resistant to electrical conductance, acidic conditions and maintains its integrity and shape at temperatures up to about C. Typical of such plastic include polyvinylchloride, post-chlorinated polyvinylchloride, fluorinated hydrocarbons, ABS polymers, epoxy polyesters and the like materials. Where metal parts are desirably used, such parts should be coated with nonconductive coatings to insulate them from the acidic environment and electrical current.

Lower enclosure 14 is conveniently merely an extension of housing 12 which is sealed at the bottom 16 thereof and is open in the upper interior portions thereof for the collection of sediment.

Electrode I8 is positioned within housing 12 and is comprised of titanium. Electrode 18 can be of any shape desired, but it is preferably to shape the electrode in a manner to maximize surface area. The embodiment illustrated in FIG. I is of cylindrical shape having an open bottom end and perforations along the sidewalls so as to provide free access of electrolyte to the interior surfaces thereof. Such perforation can be designed to increase surface area while permitting electrolyte to circulate to the interior walls of electrode 18, thereby utilizing the interior walls as electrolyzing surfaces.

Since the electrode assembly of the present invention is preferably utilized as a cathode, metal ions migrate to the electrode with the application of a decomposition voltage wherein they receive electrons and are converted to the free metals. With cathode metals other than titanium, the metal ions migrating thereto would normally adhere and plate onto the cathode as a free metal. This, however, does not occur with titanium. The particular cathode is therefore designed to permit free metal to settle downwardly as a precipitate into lower enclosure 14. As such, electrode 18 is preferably designed to be open-ended at the bottom thereof to permit free metals to settle out of contact with the electrode itself.

lnner housing 20 is positioned within electrode 18 so as to form a chamber for the feeding and withdrawal of electrolyte and the recovery of sediment from lower enclosure 14. Inner housing 20 is preferably a cylindrical, nonporous, rigid plastic tube which contains therein compressed air line 22, electrolyte and sediment removal line 24 and electrolyte return line 26. The particular number of lines and the particular circulatory system utilized can be varied depending on various factors such as the sediment removal and electrolyte circulatory systems desired. For instance, it is often preferred to utilize an air pump to remove sediment from lower enclosure 14 by means of feeding compressed air through line 22 via the bottom of enclosure 14 into electrolyte and sediment removal line 24. Such means creates an airlift which draws sediment and electrolyte out of lower enclosure 14 to the surface for subsequent processing. Alternatively, other pumping means such as a diaphragm pump, displacement pump, Moino pump or the like can be used to draw electrolyte and sediment through line 24 to the surface of the earth for further processing. In such instances, line 22 is used for the return of electrolyte to the electrode assembly. Other pumping arrangements can be used or substituted in whole or part as will become apparent to those skilled in the art. Where these circulatory lines are not adopted for the removal or release of generated hydrogen gas, as in those processes wherein such gases are generated, such additional gas release means are also provided.

Collar 28 is positioned in the upper portion of electrode assembly to retain seal 30. Seal 30 and collar 28 are designed to fit the well or shaft into which electrode assembly 10 is positioned. They are therefore of a size to approximate the hole or shaft diameter such that when in position, seal 30 can be expanded to form a watertight seal between the shaft wall and the electrode assembly. A convenient arrangement for providing such a seal is to utilize an expandable elastomeric material to form seal 30. Such material can be expanded in place by means of air pressure similar to the expansion ofa rubber inner tube. As such, line 32 is utilized for expanding seal 30 in place. Alternatively, seal 30 can be composed of foamed elastomeric material such as polyurethanes, foamed rubber and the like elastomeric materials which can be foamed or expanded in place or utilized in conjunction with compressed air expandable seals.

In addition to the various feed lines described herein being connected between electrode assembly 10 and the surface of the earth, electrode cable 34 is connected to a source of electrical energy, such as a generator, on the earths surface. Such electrode cable can also serve the dual function of providing a means for the raising and the lowering of the electrode into the well or shaft 36. Additionally, the various circulatory lines associated with the electrode assembly are preferably comprised of flexible plastic material as opposed to the electrode housing 12, lower enclosure 14 and inner housing 20 which are of rigid plastic materials.

In the operation of the electrolysis, the electrode assembly is positioned within shaft 36 and sealed by means of seal 30 and collar 28 to form an electrolyte chamber 38. The electrolyte chamber is filled with electrolyte solution. A positive source of direct current is attached in electrical contact to the sulfide ore body. A negative source of direct current is attached to the electrode assembly of the present invention. The sulfide ore serves as the anode when a decomposition voltage is applied. ln the electrolysis, the sulfide ore is decomposed with a corresponding enlargement of chamber 38.

The decomposition voltage is applied to preferably maximize economic current efficiencies and the most rapid decomposition of the sulfide ore. The particular current density utilized can be varied depending upon the particular metal values being recovered and the particular sulfide ore being decomposed.

As the electrolysis proceeds, metal ions go into solution in the electrolyte and migrate to the cathode where they are reduced to the free metal on the surface of the cathode. Because the formed metal does not readily adhere to the titanium cathode surface, it precipitates in finely divided form and is collected in lower enclosure 14. Electrolyte circulatory means 24 and 26 are operated either continuously or intermittently to maintain the desired electrolyte conditions of concentration, pH and the like while removing to the earths surface the metal values generated.

With the electrode assembly of the present invention, the electrolysis can be carried out continuously for indefinite periods of time with minimum requirements of attention and/or maintenance.

While there have been described herein more particularly the preferred embodiments of the present invention, it will be readily recognized by those skilled in the art that various modifications of the present apparatus can be made without departing from the spirit of the invention. As such, it is intended to cover the invention broadly, being limited only by the following claims.

What is claimed is:

1. An electrode assembly for the extraction of metal values from earth held deposits comprising a shaped structure of titanium having electrical connecting means for the passage of electrical energy to said titanium structure, said structure being enclosed within a perforated, nonconductive housing, said housing having a lower nonperforated enclosure for the collection of sediment, said enclosure having means for withdrawing sediment therefrom on a continuous or intermittent basis.

2. The apparatus of claim 1 wherein the withdrawing means is located near the bottom of the enclosure so as to withdraw sediment therefrom.

3. The apparatus of claim 1 wherein the withdrawing means IS an air pump.

4. The apparatus of claim 1 wherein the withdrawing means is a displacement pump.

5. The apparatus of claim 1 wherein the withdrawing means is a diaphragm pump.

6. The apparatus of claim 1 wherein the perforated nonconductive housing is comprised of rigid plastic.

9. The apparatus of claim 1 wherein said electrode assembly has electrolyte feed means for the feeding of electrolyte to the electrolysis area.

10. The apparatus of claim 1 wherein the titanium electrode is cylindrical in shape and has perforations therein for the circulation of electrolyte to the interior surfaces of said cylindrical electrode. 

1. AN ELECTRODE ASSEMBLY FOR THE EXTRACTION OF METAL VALUES FROM EARTH HELD DEPOSITS COMPRISING A SHAPED STRUCTURE OF TITANIUM HAVING ELECTRICAL CONNECTING MEANS FOR THE PASSAGE OF EELECTRICAL ENERGY TO SAID TITANIUM STRUCTURE, SAID STRUCTURE BEING ENCLOSED WITHIN A PERFORATED, NONCONDUCTIVE HOUSING, SAID HOUSING HAVING A LOWER NONPERFORATED ENCLOSURE FOR THE COLLECTION OF SEDIMENT, SAID ENCLOSURE HAVING MEANS FOR WITHDRAWING SEDIMENT THEREFROM ON A CONTINUOUS OR INTERMITTENT BASIS.
 2. The apparatus of claim 1 wherein the withdrawing means is located near the bottom of the enclosure so as to withdraw sediment therefrom.
 3. The apparatus of claim 1 wherein the withdrawing means is an air pump.
 4. The apparatus of claim 1 wherein the withdrawing means is a displacement pump.
 5. The apparatus of claim 1 wherein the withdrawing means is a diaphragm pump.
 6. The apparatus of claim 1 wherein the perforated nonconductive housing is comprised of rigid plastic.
 7. The apparatus of claim 1 wherein the electrode assembly has seal means on the upper portion thereof, said means being adaptive to seal said electrode assembly and electrolyte in a reservoir of electrolyte beneath the earth''s surface.
 8. The apparatus of claim 7 wherein the seal means is an expandable collar which, when expanded, forms a liquid tight seal.
 9. The apparatus of claim 1 wherein said electrode assembly has electrolyte feed means for the feeding of electrolyte to the electrolysis area.
 10. The apparatus of claim 1 wherein the titanium electrode is cylindrical in shape and has perforations therein for the circulation of electrolyte to the interior surfaces of said cylindrical electrode. 